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The performance of B3-LYP density functional theory in describing SN2 reactions at saturated carbon |
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| Authors: | Mikhail N Glukhovtsev Robert D Bach Addy Pross and Leo Radom |
| Institution: | a Department of Chemistry, Wayne State University, Detroit, MI 48202, USA b Department of Chemistry, University of Delaware, Newark, DE 19716, USA c School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia d Department of Chemistry, Ben Gurion University, Beer Sheva, Israel e Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia |
| Abstract: | The performance of the B3-LYP variant of density functional theory when used in conjunction with the 6-31G(d) and 6-311 + G(3df, 2p) basis sets in describing the prototypical gas-phase SN2 reactions of Cl− + CH3Cl and CH3Br has been examined in detail. Reasonable values of the complexation energies (ΔHcomp) for the ion-molecule complexes formed in these reactions are obtained. However, the overall (ΔHovr#) and central (ΔHcent#) barriers for these reactions calculated using the B3-LYP functional are significantly underestimated when compared with G2(+) or experimental results. This implies that the B3-LYP energies for the Cl(H3C)Cl− (D3h) and Cl(H3C)Br− (C3v) transition structures are relatively too low. The B3-LYP errors appear to be systematic, with similar errors being found for corresponding quantities for the two reactions examined. |
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